St. Martin is a census-designated place (CDP) in Jackson County, Mississippi, United States.

As of the 2020 United States census, there were 7,811 people, 2,977 households, and 1,645 families residing in the CDP.

18.6% of all households were made up of individuals, and 7.5% had someone living alone who was 65 years of age or older.

The Jackson County Sheriff's Office provides law enforcement services for the community.

St. Martin is served by the Jackson County School District.

St. Martin is also home to a branch of the Jackson-George Regional Library, located at 15004 LeMoyne Boulevard.